This study will investigate the molecular mechanism(s) by which transposable elements activate gene expression in Pseudomonas cepacia. P cepacia is a bacterium noted for its ability to catabolize a wide variety of growth substrates (1,25), and for its effectiveness as both an opportunistic human pathogen (8,10) and a phytopathogen (1). A recent study proposes that the activation of gene expression by transposable elements in P. cepacia is one means employed by the bacterium to increase its adaptability (24). Five transposable elements were identified which insertionally activated a beta-lactamase gene introduced into P. cepacia on a broad host range plasmid (24). The proposed study seeks to elucidate the mechanism(s) of beta-lactamase gene activation. This will require: 1) DNA sequence analyses to further characterize the elements and to determine the precise location of each of the insertions 2) Northern hybridization experiments to determine the seize and abundance of the beta- lactamase mRNAs produced as a result of activation and, 3) S1 nuclease mapping experiments to position the beta-lactamase transcripts on the known DNA sequence. The result of this investigation will provide valuable insights into the regulatory signals which govern gene expression in P. cepacia.